Heart Scales are amongst the most coveted items that can be found and used by the player in Pokemon X and Y. They are important because they enable you to teach your Pokemon moves that they’ve forgotten. This is so that if you had to overwrite an important move you can relearn it easily.
Collecting Heart Scales can be pretty difficult, but if you have the knowledge on how to maximize your chances for finding one, it can become much easier than you might think. The best method for finding them are by farming Luvdisks by fishing for them.
Here’s what you need to do; you’ll need at least two pokemon, and a fishing pole (the Old Rod will do just fine).
Your first Pokemon must have the Compound Eyes Ability, so I recommend a Vivillion. This will increase your chances of finding a wild Pokemon with an equipped item. In the second slot you need to have a Pokemon with the Frisk ability that can also learn the TM ‘Thief’.
For this second one I recommend Noibat or something. The Frisk ability makes it so that it will examine the enemy Pokemon and identify what item it’s holding. Then you can use the Thief ability to steal it.
Now the trick is to put your Vivillion in the first slot, but reduce its HP to zero first.
What this does is that because it’s in the first slot, it’s Compound Eyes ability is in effect, increasing your chances of finding a Pokemon with an item. However, when you enter battle, you’ll throw out your second Pokemon with the Frisk and Thief (because the first one is fainted), enabling you to quickly identify if the Luvdisk has a Heart Scale and steal it.
As a final note, a good place to fish for Luvdisks is right outside where you find the Old Rod.